1. Field of the Invention
Aspects of the invention relate to optical navigation using a microlens array, and more particularly, to an electronic device having an integrated optical navigation module using a flat-type microlens array.
2. Description of the Related Art
Conventionally, navigation modules (i.e., computer mice) come in a wide variety of shapes having different features, sizes and prices. Navigation modules are categorized according to how the motion is sensed. Specifically, optical navigation modules use optical motion sensing. In contrast, mechanical navigation modules use mechanical motion sensing. While the mechanical mice were the earlier of the two types of navigation modules, the optical navigation modules have begun to gain increased acceptance.
Early versions of optical navigation modules were used in the context of personal computers and relied upon fine lines on a specific grid in order to perform tracking operations. However, with the advent of an optical position sensor by Agilent Technologies in 1999, optical mice are now able to work on a wide variety of surfaces without requiring the fine line grids. The optical position sensor works by taking a picture of the surface on which the mouse is navigating, and comparing images taken sequentially to detect the speed and direction of the movement of the surface relative to the mouse. In this manner, the optical mouse is able to navigate across a wide variety of surfaces without requiring such a grid.
In contrast to early optical mice and mechanical mice which used a ball to perform the tracking operation, an optical mouse typically does not use a ball. Specifically, the mouse includes a clear lens underneath. Light from a light source (generally an LED emitting a red wavelength light) reflects off the surface and is received through a window at the lens. The lens focuses the received light on a sensor, which detects the image. As such, as the mouse is moved, the sensor takes continuous images of the surface and compares the images to determine the distance and direction traveled utilizing digital signal processing. The comparison results are then sent to a personal computer in order to move the cursor on the screen.
With the emergence of increasing numbers of handheld electronic devices, such as cell phones and PDAs, with small displays and increased functionality, there is an increased need for more flexible and sophisticated navigation technologies to allow the user to easily access this functionality. However, while optical mice are used with computers, optical navigation modules are not used for these handheld devices. This is because computers are of a larger scale and are expected to use external optical mice on a desk in order to navigate on a screen. In contrast, handheld devices have a constrained size so as to fit in the hand and/or pocket. Thus, handheld devices are not typically used with external devices to perform on-screen navigation, making the inclusion of conventional optical navigation technologies impractical with the handheld devices.
Instead, conventional handheld devices, such as cell phones and personal digital assistants (PDAs), use mechanical navigation devices to perform on screen navigation. Examples of mechanical navigation devices include a button, rocker switch, a click wheel, and/or touch screen displays. As such, when a user needs to select an item or navigate through an on screen menu, the user presses the button, rocker switch and/or presses (such as with a stylus) the screen itself.
However, such mechanical devices have drawbacks in terms of overall aesthetic appeal, are liable to wear out from prolonged use, and are limited in terms of the navigation directions. For instance, on a cell phone using the rocker switch, the rocker switch is under a circular disk and typically allows navigation in one of four directions (i.e., up/down and left/right). As such, when pressed by the user, the user can only navigate in one of the four directions. Therefore, in order to increase range of on screen movement, there need to be increased numbers of switches, which increases the complexity of the navigation module and exacerbates space constraints in a typical hand held device. Thus, existing rocker switch technology is not suitable for providing cursor movement similar to that performed on computers using mice.
For other technologies such as that used in BLACKBERRIES and IPODs, a mounted track wheel is used to allow rapid up-down cursor navigation. However, the track wheel allows only one dimensional movement, and does not allow left-right (i.e., two dimensional) navigation.
Moreover, mechanical devices such as buttons, rocker switches and sidewalls have drawbacks in terms of overall aesthetic appeal, and are liable to wear out from prolonged use.
Additionally, while touch screen technology allows increased cursor motion, the user is typically is forced to obstruct the display itself to perform navigation. While suitable for desktop computer screens, this obstruction is problematic for small displays. Thus, when used in a handheld device such as a PDA, a separate stylus is often used for increased cursor movement accuracy. The use of the stylus has drawbacks in that the stylus is easy to misplace, aggravating the user. Moreover, unless a stylus is used, the display is likely to become dirty as users touch the display to navigate thereon. Thus, touch screen technology also has limitations when used in the context of navigating cursors.